1. Field of the Invention
The present invention relates to a cut-sheet feeding apparatus, a document feeding apparatus, and a document-sheet reading apparatus.
2. Description of Related Art
There is widely known an image, processing apparatus, such as a scanner, a copier, a facsimile machine, or a multifunction apparatus having two or more of a scanner function, a copier function, and a facsimile function, which includes a cut-sheet feeding apparatus that automatically picks up a plurality of cut sheets such as recording sheets or document sheets set on a setting portion or a supply tray to one by one supply the cut sheets into a feed path. Each cut sheet is then fed along the feed path down to an ejecting portion or a catch tray, onto which the cut sheet as having been fed is ejected, via a reading position or a recording position. For instance, the cut-sheet feeding apparatus may be an ADF Automatic Document Feeder) included in an image reading apparatus to feed document sheets to be read, or a recording-medium feeding apparatus included in an image recording apparatus to feed recording media on which an image or information is to be recorded.
There will be briefly described a known ADF as a kind of the cut-sheet feeding apparatus, which includes a supply tray, a catch tray, a pickup portion, and a feeding portion. Document sheets, with images to be read thereon, are set on the supply tray. The pickup portion picks up the document sheets one by one from the supply tray and feeds each document sheet into a feed path, along which a reading position at which the document sheet is read is located. The feeding portion operates to feed the document sheet along the feed path, so that each document sheet is read at the reading position and further fed along the feed path down to the catch tray at an end of the feed path. That is, after read, the document sheet is ejected onto the catch tray.
The pickup portion includes a pickup chute formed continuously with the supply tray, a pickup roller, a pickup nipper, a separating roller, and a separating nipper. The pickup roller is rotatably disposed on a lower guide surface of the pickup chute. On an upper guide surface of the pickup chute that is opposed to the pickup roller, the pickup nipper is disposed such that the pickup nipper is capable of moving onto and away from the pickup roller, and held biased by a spring member against the pickup roller so that the pickup nipper and the pickup roller are in direct pressing contact with each other while not nipping a document sheet therebetween.
When a stack of document sheets are set on the supply tray, a part of the stack is disposed between the pickup nipper and the pickup roller, such that the stack is biased onto the pickup roller by the pickup nipper. A lowermost one of the document sheets that is in direct pressing contact with the pickup roller receives a rotation force of the pickup roller to be fed along a supply direction, that is, picked up out of the supply tray into the feed path.
The separating roller is rotatably disposed on the lower guide surface of the pickup chute, with an interval from the pickup roller in the supply direction. On the upper guide surface of the pickup chute, the separating nipper is disposed to be capable of moving onto and away from the separating roller, and held biased by a spring member against the separating roller so that the separating nipper and the separating roller are in direct contact with each other while not nipping a document sheet therebetween. The document sheet fed into the feed path by the pickup roller is nipped between the separating roller and the separating nipper, thereby receiving a rotation force of the separating roller to be further fed along the supply direction.
The feeding portion is disposed on the downstream side of the pickup chute, and includes a pair of feed rollers, namely, a feeder roller and a pinch roller disposed adjacent thereto. The pair of feed rollers is disposed along the feed path, which is substantially U-shaped in cross section. The pinch roller is held biased onto the feeder roller and rotated with rotation of the feeder roller. Thus, while not nipping a document sheet therebetween, the pinch roller and the feeder roller are held in direct pressing contact with each other.
The document sheet fed into the feed path is nipped between the rotating feeder roller and pinch roller to be fed along the feed path. The feed path is open downward at a reading position, which corresponds to a reading surface in a platen glass under which an image scanner or an image reading device is disposed. That is, the feed path includes an open portion at a bottom surface of a cover body or a document cover. The document sheet is guided by a guide member to the open portion of the feed path so that the image reading device reads the document sheet as passing over the platen glass. The document sheet having been read is further fed from the open portion along the feed path to be eventually ejected onto the catch tray.
Where a paper jam occurs such that a document sheet is caught in the feed path in the ADF, the caught document sheet is being nipped between the feeder roller and the pinch roller since the feeder roller and the pinch roller are held against each other. Thus, it is impossible to remove the document sheet from the feed path without damaging the document sheet, unless the pressing contact between the feeder roller and the pinch roller is eliminated.
It is known to prevent such a problem by providing an arrangement for eliminating pressing contact between a feeder roller and a pinch roller to release a sheet nipped therebetween by imparting a force to separate the feeder roller and the pinch roller from each other. For instance, such an arrangement is disclosed in the following publications: JP-A-5-6123 (publication 1) and JP-A-5-155463 (publication 2).
The publication 1 discloses a recording-medium feeding apparatus including a lever with which a cam is integrally formed. When the lever is manipulated, the cam presses a shaft of one of a pair of feed rollers to eliminate pressing contact between the feed rollers.
The publication 2 discloses to dispose a pinch roller on an end portion of a plate member that is supported at an intermediate portion thereof such that the plate member is capable of swinging around the supported portion. By pushing up an end portion of the plate member opposite to the end portion on which the pinch roller is disposed, the pinch roller is separated from the feeder roller.
Further, techniques related to the present invention are disclosed in the following publications also: JP-U-5-61153 (publication 3), JP-U-7-157132 (publication 4), and JP-B2-3660859 (publication 5).
The publication 3 discloses a device for removing a document sheet caught in a facsimile machine. The eliminating device includes a cam mechanism that operatively associates an action of opening a cover body for opening a feed path of an ADF, with an action of pushing down a shaft of a pinch roller. Hence, when a user desiring to remove a caught document sheet opens the cover body, the pinch roller is automatically pushed down and separated from a feeder roller.
The publication 4 discloses a recording-medium feeding apparatus including two movable sheet guides each of which supports a pinch roller that is biased to be held in pressing contact with a feeder roller. When a first one of the sheet guides is moved to separate the pinch roller from the corresponding feeder roller, a second sheet guide is automatically moved to separate the pinch roller supported by a second one of the sheet guides from the corresponding feeder roller.
The publication 5 discloses a document-sheet feeding apparatus constructed such that when a document sheet is caught in a feed path while being fed along a platen glass, a document cover or a cover body is moved to its opened position, and then an auxiliary frame pivotally attached to a bottom portion of the cover body and supporting a pinch roller is moved to its opened position, whereby pressing contact between a feeder roller and the pinch roller is eliminated.
As described above, the known ADF is constructed such that when a document sheet is read, the document sheet is fed along the feed path, during which the document sheet is once fed out of the cover body at the open portion of the feed path so that the document sheet is fed over and along the platen glass at the open portion of the feed path. Then, the document sheet is fed back into the cover body. Even if the technique of any one of the publications 1-5 set forth above is employed in the ADF, removal of a document sheet caught at or around the open portion of the feed path involves (i) opening the cover body or document cover covering the platen glass, and (ii) eliminating the pressing contact between the feeder roller and the pinch roller. That is, at least two actions are required to take the caught document sheet out of the apparatus from the open portion of the feed path. However, when a document sheet caught at or around the open portion disposed at the bottom surface of the document cover should be removed, a user may feel that it is cumbersome to take the above-mentioned two actions, or may not know the way to eliminate the pressing contact between the feeder roller and the pinch roller, or the way to separate the feeder roller and the pinch roller from each other. In the former case, that is, when the user feels that taking the two actions is cumbersome, he or she may first open the document cover to expose a part of the document sheet to the exterior, and then forcibly pull out the document sheet pinched between the feeder roller and the pinch roller. The forcibly pulling out the document sheet pinched between the feeder roller and the pinch roller that are held in pressing contact with each other may damage the document sheet. In the latter case, that is, when the user does not know the way to eliminate the pressing contact between the feeder roller and the pinch roller, it takes much time to remove the caught document sheet.